This invention relates to a digital fader or like device having slidably operable means whose setting is represented by a digital signal and, more particularly, wherein adjustments to the setting are reflected by adjustments in the digital signal, which signal may be used to selectively energize a display, or may be recorded, or may be otherwise utilized.
Manually adjustable devices, such as slide resistors, potentiometers, rheostats, and the like, conventionally are used to set and vary characteristics of diverse type. For example, such devices may be manually operated to establish the gain or attenuation of a signal, to select a particular frequency and to control numerous other functions. In audio signal processing applications, the gain or level of an audio signal may be set and adjusted so as to effect a desired volume control.
In some applications, such as in some audio signal processing applications, it is desirable that the setting of a gain or volume control device be stored for utilization at a subsequent time. This is particularly useful for audio engineers and technicians who operate audio mixers. As is known to those of ordinary skill in the art, an audio mixer is a multi-channel device wherein different channels of audio signals are supplied to respective, individual inputs, each channel being subjected to independent amplification or volume control, filtering, and ancillary processing to create desired sound effects. The processed channels then are recorded in individual tracks on a record medium, such as a magnetic tape. Subsequently, the audio signals recorded in the individual tracks are reproduced and blended together, or "mixed" to create a master tape which then may be used to produce replica tapes or phonograph discs.
When using a mixer, the operator typically effects continual adjustment of the various volume control devices while recording a single "pass" or "take" of a musical performance. Hence, an individual volume control device, or fader, will have its setting changed virtually continually. Of course, at the completion of the recording of a pass, the setting of the fader will be quite different than that at the beginning of the pass. When another pass is to be recorded, either in its entirety or selected portions thereof, it is important that the operator be apprised of the setting of the fader during the previous pass so that this setting can be duplicated quickly and easily for the next recording or for an editing or re-dubbing operation. This is because, in editing and re-dubbing, it is best to be able to duplicate the previous settings and then, if the operator so desires, to vary or adjust the fader during the next pass.
In recording audio signals processed by a mixer, in addition to recording the audio signals in separate tracks, the volume or gain control as established by the fader also is recorded. For example, when using a multiple of faders, the volume setting established by such faders may be multiplexed and recorded in a single track of a record medium. Alternatively, the volume setting of each fader may be recorded periodically, or multiplexed with the audio signal whose characteristic is controlled by that fader, in the very same track as the audio signal itself. When the record medium is reproduced, the volume settings of the individual faders also are reproduced. This reproduced volume setting information is used by the operator to reset the fader at the same position as was used during the previously recorded pass, thereby establishing the same volume control as before. This resetting of the fader is, however, relatively laborious and is not easily carried out except by a skilled technician. This is because, during a reproducing operation, the actual volume setting that had been recorded and is now reproduced from the tape is compared to the present volume setting of the fader. When the present setting becomes equal to the previously recorded setting, a "null" display light is triggered. Typically, to achieve this null indication, a number of reproducing operations must be carried out repeatedly so that the fader can be adjusted to match the setting which had been recorded.